It is common for a marine engine to be provided with a water pump which draws water from outside of the hull of the operatively associated marine vehicle and pumps the water through a water jacket defined by the engine block in order to cool the engine. The water which has been pumped through the engine block generally exits the engine through the exhaust manifold of the engine. As a consequence of the dumping of cooling water into the exhaust manifold, marine mufflers have been designed which utilize the used cooling water to cool the exhaust gases exiting the exhaust manifold and to attenuate engine noise. In this regard, such marine mufflers commonly include a muffler body defining an internal cavity for receiving both the hot exhaust gases and the cooling water ejected from the manifold. At least one outlet passageway is provided which has an inlet port proximate the bottom of the cavity and an outlet port which is exterior to the muffler body. Cooling water exiting the exhaust manifold collects in the bottom of the cavity of the muffler body, such that the inlet port of the outlet passageway is submerged in water. Pressure within the cavity from the injection of exhaust gases forces the exhaust gases through the water and forces both the exhaust gases and water through the outlet passageway and out of the muffler body. The forcing of the exhaust gases through the used cooling water serves to both cool the gases and to attenuate engine noise. Examples, of mufflers and exhaust systems utilizing this concept are disclosed in U.S. Pat. Nos. 5,259,797; 5,147,232; 5,045,005; 4,917,640; 4,713,029; 3,296,997; 2,498,979; and 2,360,429.
Recently marine engines have been produced in which the used cooling water is pumped into an outlet conduit which directs the used cooling water out of the hull of the marine vehicle. Thus, little or no cooling water is dumped into the exhaust manifold of the engine. By diverting the used cooling water rather than directing it into the exhaust manifold, back pressure on the engine is reduced, and the engine runs more efficiently. Certain jet ski engines utilize this technique to enhance the power of the small engines which they utilize, and the technique can be advantageous in various marine engine applications. However, where the cooling water is directed out of the engine and through the hull, rather than through the exhaust system, little or no water is provided to the muffler to cool the exhaust or to muffle engine noise. Accordingly, conventional marine mufflers which utilize water to cool the exhaust gases and attenuate engine noise do not function properly. Of course, a different type of muffler can be used, such as a muffler of the type used on automobiles, but the advantages of cooling of the exhaust gases with water are lost.
Therefore, it is an object of the present invention to provide a marine engine exhaust system and method which utilizes water to cool the exhaust gases and to attenuate engine noise, but which is not dependant upon a supply of used engine cooling water from the engine exhaust manifold for operation.
Yet another object of the present invention is to provide a marine engine exhaust system which utilizes the water pump of the marine engine to supply water to the exhaust system such that a separate water supply mechanism is not required.
It is another object of the present invention to provide a marine engine exhaust system which is inexpensive to manufacture and maintain.